/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;

import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Bimap with zero or more mappings.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class RegularImmutableBiMap<K, V> extends ImmutableBiMap<K, V>
{
    static final RegularImmutableBiMap<Object, Object> EMPTY = new RegularImmutableBiMap<>();

    @CheckForNull
    private final transient Object keyHashTable;
    @VisibleForTesting
    final transient @Nullable
    Object[] alternatingKeysAndValues;
    private final transient int keyOffset; // 0 for K-to-V, 1 for V-to-K
    private final transient int size;
    private final transient RegularImmutableBiMap<V, K> inverse;

    /**
     * Constructor for empty bimap.
     */
    @SuppressWarnings("unchecked")
    private RegularImmutableBiMap()
    {
        this.keyHashTable = null;
        this.alternatingKeysAndValues = new Object[0];
        this.keyOffset = 0;
        this.size = 0;
        this.inverse = (RegularImmutableBiMap<V, K>) this;
    }

    /**
     * K-to-V constructor.
     */
    RegularImmutableBiMap(@Nullable Object[] alternatingKeysAndValues, int size)
    {
        this.alternatingKeysAndValues = alternatingKeysAndValues;
        this.size = size;
        this.keyOffset = 0;
        int tableSize = (size >= 2) ? ImmutableSet.chooseTableSize(size) : 0;
        this.keyHashTable =
                RegularImmutableMap.createHashTable(alternatingKeysAndValues, size, tableSize, 0);
        Object valueHashTable =
                RegularImmutableMap.createHashTable(alternatingKeysAndValues, size, tableSize, 1);
        this.inverse =
                new RegularImmutableBiMap<V, K>(valueHashTable, alternatingKeysAndValues, size, this);
    }

    /**
     * V-to-K constructor.
     */
    private RegularImmutableBiMap(
            @CheckForNull Object valueHashTable,
            @Nullable Object[] alternatingKeysAndValues,
            int size,
            RegularImmutableBiMap<V, K> inverse)
    {
        this.keyHashTable = valueHashTable;
        this.alternatingKeysAndValues = alternatingKeysAndValues;
        this.keyOffset = 1;
        this.size = size;
        this.inverse = inverse;
    }

    @Override
    public int size()
    {
        return size;
    }

    @Override
    public ImmutableBiMap<V, K> inverse()
    {
        return inverse;
    }

    @SuppressWarnings("unchecked")
    @Override
    @CheckForNull
    public V get(@CheckForNull Object key)
    {
        Object result =
                RegularImmutableMap.get(keyHashTable, alternatingKeysAndValues, size, keyOffset, key);
        /*
         * We can't simply cast the result of `RegularImmutableMap.get` to V because of a bug in our
         * nullness checker (resulting from https://github.com/jspecify/checker-framework/issues/8).
         */
        if (result == null)
        {
            return null;
        }
        else
        {
            return (V) result;
        }
    }

    @Override
    ImmutableSet<Entry<K, V>> createEntrySet()
    {
        return new RegularImmutableMap.EntrySet<K, V>(this, alternatingKeysAndValues, keyOffset, size);
    }

    @Override
    ImmutableSet<K> createKeySet()
    {
        @SuppressWarnings("unchecked")
        ImmutableList<K> keyList =
                (ImmutableList<K>)
                        new RegularImmutableMap.KeysOrValuesAsList(alternatingKeysAndValues, keyOffset, size);
        return new RegularImmutableMap.KeySet<>(this, keyList);
    }

    @Override
    boolean isPartialView()
    {
        return false;
    }
}
